In the boring of vertical and non-vertical holes in the earth for the placement of support structures such as pilings, the common practice is to use vertical power driven augers to bore into the earth formation. These augers are usually rotatably suspended from a drilling mast attached to the rear of a truck. A serious disadvantage to the auger system is its inability to accurately bore piling holes in sloping and uneven grounds. For instance, in the building of bridges and other sophisticated projects such as the Alaskan pipeline project, piling support holes must be drilled through the ground in rough terrain while maintaining a vertical accuracy of three inches in a borehole fifty feet deep. Also as in the case of the Alaskan pipeline, the boreholes must be drilled with a minimum amount of damage to the earth formation being penetrated. For instance, when the holes are drilled in tundra and frozen ground, extreme care must be taken to prevent thawing of the ground surrounding the borehole and care must be taken to prevent scarring of the surface of the tundra by the drilling vehicle.
The present state of auger drilling does not provide nearly enough accuracy to drill within three inches in a fifty foot deep borehole. Furthermore, the auger type of drill is very damaging to the formation and the tundra in that it thaws the tundra and must also be removed very frequently to remove cuttings which accumulate within the auger flutes.
The present invention overcomes these difficulties by providing a portable rig system rotatably mounted on a tracked vehicle having automatic power alignment means for obtaining extremely accurate alignment of the drill and mast over the boring site.